Considering their signature dish is a filet mignon with mushrooms, risotto, and truffle butter sauce, I think you're being a bit harsh. Of course it's not Craftsteak or Bern's, but Via Napoli isn't Scarpetta and Bistro de Paris isn't Le Bernardin either.
The bottom line, IMO - Le Cellier lunch is an excellent value if you're on the dining plan. You can get filet mignon, and even a sauce with truffle flavor (truffle anything for 1 credit is a good deal). Combine that with the comforting yet slightly unique cheddar cheese soup and maple crème brûlée that have both established cult followings, as well as a fairly decent menu and the restaurant's small size, and that's exactly why Le Cellier has become so popular.
IMO, the food is very good for theme park standards. Most restaurants in Epcot don't come close (definitely not Coral Reef, and I'm a seafood person, definitely not Garden Grill, not Nine Dragons, Les Chefs, Marrakesh, etc). Bistro de Paris has the best food quality in Epcot, but it's a lengthy meal with upscale food that many people don't really want. Le Cellier definitely has broader appeal, but I still think its food quality is up there (the only theme park restaurant I like more is Brown Derby).
More info: I'm not a picky eater - there are a few things I just don't like, but I'll eat any type of food: South African, Moroccan, Ethiopian, Chinese, Japanese, Korean, Thai, Vietnamese, Malaysian, Indian, Italian, French, Mexican, Spanish, Cuban, seafood, spicy, etc. So I definitely wouldn't put myself in the "meat and potatoes" box. That said, I still think Disney dining isn't exactly stellar, and Le Cellier is easily one of the better options available in the parks. Any comparison you make between a Disney restaurant and a similarly priced restaurant in the real world is likely to not end in Disney's favor.
I get what you're saying, and you make some valid points. But I think I was being generous, not harsh.
I don't think Les Cellier is horrible, just not good.
I had the truffle filet. I found it to be a very mediocre piece of meat -- what you can get fairly cheaply at any supermarket. Certainly didn't have the flavor of free range or grassfed beef. And coating a mediocre piece of meat in truffle flavored butter does not elevate it. It's more like fake gourmet, by using the word truffle. I found the whole dish to be heavy handed, poorly seasoned, just a mess really.
But I did think the mushroom risotto was fairly good. Could have been a bit creamier. And I had a duck meatball appetizer that really was very good.
Now, I wouldn't expect a theme park restaurant to match up to Berns or Craft...
But in terms of steak, it didn't even match up to a Morton's or Ruth's Chris, in my opinion. I can't speak to every restaurant at Epcot. But for example, I did find Via Napoli pizza to be well above average. California Grill sushi isn't Masa, but it is above average sushi. The lobster at Narcoose's doesn't match Les Bernadin, but it compares well to Legal Seafood.
So while I don't dislike Les Cellier -- it's not on my 'avoid' list -- I just see many far more interesting options, that better execute their specialty.